Multi-primary backlight for multi-functional active-matrix liquid crystal displays

ABSTRACT

A direct view display provides a light modulating panel and a backlight including first and second sets of spectral emitters. Several modes of operation may be provided including an advanced 2D mode, and an enhanced color gamut mode employing simultaneous illumination of the first and second set of spectral emitters. Another embodiment may be an optical structure for a multi-functional LCD display with wide color gamut and high stereo contrast. The optical structure may also be used to produce more saturated colors for a wider display color gamut and also may be used to produce a brighter backlight structure through light recycling of the wider bandwidth light back into the optical structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to U.S. Pat. No. 8,233,034, filed Feb. 9, 2007,entitled “Multi-functional active liquid crystal displays”, the entiretyof which is herein incorporated by reference.

TECHNICAL FIELD

Disclosed embodiments herein relate generally to direct-view liquidcrystal displays (LCDs), and more particularly, to processes,architectures and techniques for achieving improved performance, newapplications, and eyewear therefor.

BACKGROUND

Advances in active matrix liquid crystal display (AMLCD) performance,particularly in television and gaming displays have been achieved by newbacklight technology and LCD display driving techniques. For instance,LEDs with improved RGB spectra have shown better gamut/efficiency overdisplays using conventional cold cathode fluorescent lamps (CCFL).

Multi-primary displays (displays with four or more primary monochromaticlight sources) have been demonstrated on several platforms, includingprojection displays and direct-view AMLCDs. For the former, Jorketeaches a split-path system with a six-primary display using adual-projector configuration in U.S. Pat. No. 6,698,890. This approachis also used to provide stereo display. Typically, such projectionsystems are considerably more hardware intensive and compromise theperformance (e.g., brightness) attainable with a conventionalthree-panel projection system.

Lamp-based six-color AMLCDs have also been demonstrated using the hybridspatial-sequential method. However, gamut enhancement is relativelymodest due to the challenges of tailoring the individual lamp emissionspectra. In some cases, (non-sequential) enhanced gamut is obtained bysimply combining CCFLs with different emission spectra.

There have been demonstrations of 3D using wavelength separation as ameans of presenting stereo imagery with a single display. So-calledanaglyph displays present the two image views by partitioning thespectrum. Typically, lenses of non-overlapping complementary color(e.g., red and cyan) are used. However, the lack of wavelengthselectivity of traditional low-cost (dye) filter technology hasprohibited the presentation of full-color information to each eye.

Another anaglyph approach involves filtering of light with greaterselectivity, such that non-overlapping spectra presented to each eyeprovide improved perception of color. In one instance, substantiallyfull color is presented to one eye, with the other receiving amonochrome image. Another technique of multiplexing involvespresentation of non-overlapping RGB content to each eye, as taught byJorke.

SUMMARY

High resolution large screen televisions and flat-screen computermonitors are successfully displacing CRT technology throughout much ofthe world. The next advancements in display performance will enable yetanother level of performance and functionality. In the case of largescreen active matrix LCD (AMLCD), technology trends are governed by therequirement of meeting, and even exceeding, the performance achievablewith plasma display technology.

The present disclosure provides a direct view display that may operateunder one or more modes of operation including (1) an advanced 2D mode,(2) an enhanced color gamut mode using six primary spectral emitters,(3) a privacy screen mode, (4) a dual-image (or channel multiplexed)mode, and (5) a stereoscopic image mode.

The present disclosure additionally provides an optical structure thatmay be used to produce two sets of colors and which may be used in astereoscopic backlit liquid crystal display. The optical structure maybe used to produce a brighter backlight structure through lightrecycling of the wider bandwidth light back into the optical structure.The optical structures may be spectrally distinct and may illuminate thesame light guide plate. The optical structures may be driven intime-sequential fashion to illuminate the light guide plate in synchronywith left and right eye images sequentially driven to the liquid crystaldisplay panel.

Furthermore, the direct view displays of the present disclosure mayovercome performance deficiencies that hamper competitiveness ofconventional AMLCD products. In the context of direct-view AMLCDdisplays, these issues include: (a) motion artifacts due to theimage-hold function of the light modulating panel; (b) limited viewangle performance: (c) head-on contrast ratio; (d) limited color gamutdue to the quality of dyes in color filter arrays, coupled with CCFLlamp spectra, (e) non-optimum power efficiency, due to non-optimumspectrum of CCFL lamps, and (f) environmental concerns regarding mercuryin CCFL lamps. Embodiments described herein may address one or more ofthese performance issues while also providing one or moremulti-functional modes. LED backlights may prove beneficial inaddressing these issues, as well as gamut enhancement, improved lightefficiency, improved contrast, content-dependent dimming, active colortemperature control, and sequential color operation.

Examples of methods, processes, architectures and techniques aredisclosed herein, but other methods, processes, architectures andtechniques can be used without departing from the spirit and scope ofthe present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example in the accompanyingfigures, in which like reference numbers indicate similar parts, and inwhich:

FIG. 1 is a schematic diagram illustrating a direct-view display systemin accordance with the present disclosure;

FIG. 2 is a schematic diagram illustrating a direct-view display systemin accordance with the present disclosure;

FIG. 3 is a schematic diagram illustrating an embodiment of an LED-basedscanning backlight, in accordance with the present disclosure;

FIG. 4A is a graph showing intensity against wavelength for first andsecond sets of spectral emitters, in accordance with the presentdisclosure;

FIG. 4B is a graph showing intensity against wavelength for filteredfirst and second sets of spectral emitters, in accordance with thepresent disclosure;

FIG. 4C is a graph showing scaled spectra for an RGB color filter arrayincorporated into a light modulating panel, in accordance with thepresent disclosure;

FIG. 4D is a graph showing spectra of first and second sets of spectralemitters through a color filter array in accordance with the presentdisclosure;

FIG. 4E is an EBU graph showing a light output set defined by an RGBtriangle in a modified color space (u′, v′), in accordance with thepresent disclosure;

FIG. 4F is a graph showing intensity against wavelength for first andsecond sets of spectral emitters, in accordance with the presentdisclosure;

FIG. 4G is a graph showing the resulting six primary color spectra ofFIG. 4F, given as the product of a particular white input spectrum witheach of the Color Filter Array spectra, in accordance with the presentdisclosure;

FIG. 4H is an EBU graph showing first and second light output setscorresponding to the spectral emitters referenced in FIG. 4G, as definedby first and second RGB triangles in a modified color space (u′, v′), inaccordance with the present disclosure;

FIG. 4I is a graph illustrating transmission profiles for an embodimentincluding first and second polarization interference filters for viewingrespective first and second images illuminated with respective first andsecond sets of spectral emitters, in accordance with the presentdisclosure;

FIG. 4J is a graph showing raw spectra from the spectral emitterstransmitted to each eye through the aforementioned polarizationinterference eyewear of FIG. 4I in accordance with the presentdisclosure;

FIG. 4K is a graph showing a scaled version of the FIG. 4J spectra,adjusted to achieve balanced white lumens and color in each eye inaccordance with the present disclosure;

FIG. 4L is a graph illustrating transmission profiles for anotherembodiment including first and second polarization interference filtersfor viewing respective first and second images illuminated withrespective first and second sets of spectral emitters, in accordancewith the present disclosure;

FIG. 5 is a schematic diagram illustrating a scanning backlight withblack-band insertion, in accordance with the present disclosure;

FIG. 6 is a logic diagram illustrating a process of black band insertionin conjunction with a scanning backlight, in accordance with the presentdisclosure;

FIGS. 7A-7H are schematic diagrams illustrating an LED-based scanningbacklight in operation, in accordance with an embodiment of the presentdisclosure;

FIGS. 8A-8H are schematic diagrams illustrating an LED-based scanningbacklight with light control films in operation, in accordance with anembodiment of the present disclosure;

FIG. 9 is a graph showing tristimulus curves describing the spectralsensitivity of three retinal sensors in a typical eye;

FIG. 10 is a schematic diagram illustrating an embodiment of a backlightstructure, in accordance with the present disclosure;

FIG. 11 is a schematic diagram illustrating another embodiment of abacklight structure, in accordance with the present disclosure;

FIG. 12 is a schematic diagram illustrating another embodiment of abacklight structure, in accordance with the present disclosure;

FIG. 13 is a schematic diagram illustrating an embodiment of non-imagingoptical element, in accordance with the present disclosure;

FIG. 14 is a schematic diagram illustrating an embodiment of an LCDtransmission compensated for tapered illumination, in accordance withthe present disclosure;

FIG. 15 is a schematic diagram illustrating an embodiment of anotherbacklight structure, in accordance with the present disclosure;

FIG. 16 is a schematic diagram illustrating an embodiment of a whitecavity assembly, in accordance with the present disclosure;

FIG. 17 is a graph illustrating a wavelength gap between a trim filterand eyewear, in accordance with the present disclosure;

FIG. 18 is a schematic diagram illustrating a reduction in leakage witha blue shift between a trim filter and eyewear transmission, inaccordance with the present disclosure;

FIG. 19 is a schematic diagram illustrating an embodiment of abuttingoptical structures and light guide plate sections, in accordance withthe present disclosure; and

FIG. 20 is a schematic diagram illustrating an embodiment of astereoscopic scrolling backlight structure, in accordance with thepresent disclosure.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram illustrating a direct-view display system100. The direct-view display system 100 includes a direct view display102 and, for viewing some modes, eyewear 104. Eyewear 104 includes lefteye and right eye filters 106, 108 respectively. Left and right eyefilters 106, 108 may include retarder stacks for decoding first andsecond light bundles emitted from the direct view display 102.

The direct view display 102 may operate under several modes of operationincluding (1) an advanced 2D mode, (2) an enhanced color gamut modeusing six primary spectral emitters, (3) a privacy screen mode, (4) adual-image (or channel multiplexed) mode, and (5) a stereoscopic imagemode. In the enhanced color gamut mode, eyewear 104 is not needed. Inmodes two through four, eyewear 104 may be used to decode an image onthe direct-view display 102. As will be appreciated with reference tothe following description, filters 106, 108 may have differentconfigurations to decode images in accordance with a mode of operation.

FIG. 2 is a schematic diagram illustrating a direct-view display 200.The direct-view display 200 includes a backlight 300, a light modulatingpanel 210, a backlight controller 220, a light modulator controller 230,a backlight power supply 240, and a mode controller 250.

When partitioning the spectrum, display performance metrics may includethe white point (and matching of white point between first and secondsets of spectral emitters), the color gamut (and matching of colorcoordinates between first and second sets of spectral emitters), and thelumens available from the first and second sets of spectral emitters.Such display performance involves complex analysis, that may includevisual perception, hardware for display imagery, the actual content, andsoftware corrections to improve matching between the output for thefirst and second sets of spectral emitters. Accordingly, temperaturecontrol of the backlight 300 may be provided via temperature sensor 222coupled to temperature feedback module 224. Whitepoint, brightness andcolor control parameters may be managed by backlight controller 220,which includes feedback for such parameters via color sensor 226 andoptical feedback module 228. Backlight controller 220 may providecontrol signals to backlight power supply 240, which provides current tospectral emitters in backlight 300. Brightness control 242 andrespective color controls 244 a-f may also provide an input to backlightcontroller 220 for adjustment of display brightness and respective colorintensity. Whitepoint control input may be received by whitepointcontroller module 232 over line 234 from light modulator controller 230.Backlight control input may be received by backlight controller module220 over line 236 from light modulator controller 230.

In this embodiment, mode selection is controlled via mode controller250, which may switch first and second input video signals 262, 264 andprovide signals to the light modulator controller 230 and backlightcontroller 220 in accordance with the selected mode. For example, in theadvanced 2D mode and the enhanced color gamut mode, a single videosignal is input to the mode controller 250. In channel multiplexed modeand the stereoscopic image mode, two video signals 262, 264 are input tothe direct view display 200. In the privacy screen mode, a single videosignal 262 may be input into the direct view display for a first image,while the second image is synthesized by an image generating function inthe mode controller 250. Image processing functions may be performed bymode controller 250 and/or light modulator controller 230. As shown,entrance polarizer 212 and exit polarizer 214 may be located on eitherside of light modulating panel 210, respectively. Thus, direct-viewdisplay 200 outputs polarized light to a viewer.

FIG. 3 is a schematic diagram illustrating an embodiment of LED-basedscanning backlight 300. Backlight 300 includes a first set of spectralemitters 310 and a second set of spectral emitters 320. As shown by thisembodiment, optically separated sub-arrays may be formed using boundarystructures 330.

In an embodiment, the first set of spectral emitters 310 are operable tooutput narrow transmission ranges R1, G1, B1; and the second set ofspectral emitters 320 are operable to output narrow transmission rangesR2, G2, B2. As shown, the spectral emitters may be arranged in rows,with columns alternating between first and second set emitters 310, 320(e.g., in the sequence R1, R2, G1, G2, B1, B2, . . . , R1, R2, G1, G2,B1, B2), however, it should be apparent that alternative sequences andphysical configurations of spectral emitters may be employed in otherembodiments. Care should be taken to control homogeneity in illuminationin the vicinity of the boundary structures 330. Uniform brightness andhue depend upon the extent of any physical gap between sub-arrays, thematching of LED luminance and chrominance in the sub-arrays, and thetiming in the driving of the sub-arrays.

The ability of the human eye to distinguish colors is based upon thevarying sensitivity of different cells in the retina to light ofdifferent wavelengths. The retina contains three types of color receptorcells, or cones. One type, relatively distinct from the other two, ismost responsive to light that we perceive as violet, with wavelengthsaround 420 nm. (Cones of this type are sometimes called short-wavelengthcones, or S cones). The other two types are closely related geneticallyand chemically. One of them (sometimes called long-wavelength cones, orL cones) is most sensitive to light we perceive as yellowish-green, withwavelengths around 564 nm; the other type (sometimes calledmiddle-wavelength cones, or M cones) is most sensitive to lightperceived as green, with wavelengths around 534 nm.

Light, no matter how complex its composition of wavelengths, is reducedto three color components by the eye. For each location in the visualfield, the three types of cones yield three signals based on the extentto which each is stimulated. These values are called tristimulus values.The response curve as a function of wavelength for each type of cone isillustrated in FIG. 9. Because the curves overlap, some tristimulusvalues do not occur for any incoming light combination. For example, itis not possible to stimulate primarily the mid-wavelength/“green” cones;the other cones will inevitably be stimulated to some degree at the sametime. The set of all possible tristimulus values determines the humancolor space. It has been estimated that humans can distinguish roughly10 million different colors.

Generally, the R1 and R2 narrow transmission ranges lie substantiallywithin the sensitive wavelengths of the L-cone receptors in a human eye(as illustrated by FIG. 9); the G1 and G2 narrow transmission ranges liesubstantially within the sensitive wavelengths of the M-cone receptorsin the human eye; and the B1 and B2 narrow transmission ranges liesubstantially within the sensitive wavelengths of the S-cone receptorsin the human eye. As used herein, the term “transmission ranges” refersto the output spectra from a spectral emitter, whether direct or as aproduct of a spectral emitter through a color filter array.

FIG. 4A is a graph showing intensity against wavelength for first andsecond sets of spectral emitters. The LED spectra for the first andsecond sets of spectral emitters (R1, R2, G1, G2, B1, B2) are scaled tounity peak emission. The center wavelengths are selected so as toprovide a high degree of spectral separation, thereby enabling thedisclosed modes of operation with little loss of light in thepartitioning process. Such separation is also beneficial in maximizingthe gamut area for the enhanced color gamut mode as well.

FIG. 4B is a graph showing intensity against wavelength for filteredfirst and second sets of spectral emitters. In this embodiment, thefirst set narrow transmission ranges (R1, G1, B1) are substantiallynon-overlapping with the second set narrow transmission ranges (R2, G2,B2). As used herein, the term “substantially non-overlapping” refers tomost of the spectral emission being independent of an adjacent emissionfrom another spectral emitter, such that cross talk between channels ispreferably minimized. It should be appreciated by a person of ordinaryskill in the art that using some off-the-shelf non-ideal spectralemitter technology, some spectral overlap may be present, for instancebetween channels B1 and G2, and channels G1 and R2, as shown by FIG. 4B.However, care should be taken in selection of spectral emitters (and insome embodiments, spectral filters) to minimize such cross-talk betweenspectral emitter channels. By careful selection of center wavelengthsfor spectral emitters, optimized color coordinates with enhanced gamutmay be obtained. It will be appreciated that other types of spectralemitters such as lasers and super resonant LEDs have a narrowertransmission range than typical LED structures, thus will be less likelyto have spectral ranges that ‘overlap.’ With sufficient“non-overlapping” wavelength separation, the demands placed on theeyewear 104 for efficient separation of imagery of first and secondspectral light sets may be relaxed. This can be contrasted withconventional UHP lamp spectra, which may use significant auxiliaryfiltering to accomplish similar performance, representing additionalcost, and loss in light efficiency.

As shown in FIG. 4B, notches ideally exist both between short/longprimary emission bands (for example, B2/B1, G2/G1, R2/R1), as well asemission bands of the other primary colors. This separation ispreferably maximized, with the understanding that the color coordinatesshould be acceptable and remain within a reasonable photopic sensitivityrange (e.g., the short blue emission B2>430 nm; the long red emissionR1<660 nm) for efficiency reasons. Such separation may accomplisheddirectly, though additional filtering that may be incorporated into thespectral emitter (for example, LED) package to provide adequate colorperformance of the display. This may include filters that eliminatereject light, or filters incorporated into the emitting structure (e.g.,Bragg reflectors) that redirect light back to the light generatingmedium. This filtering may have little influence on efficiency, providedthat the main emission lobe is substantially captured, and the tail ofthe emission is attenuated. The tail can be relatively broad, and whileit contains relatively little power, it can have significant impact onghost images when operating in stereo-mode. Such tail emissioncontributes directly to cross-talk and is independent of the performanceof the eyewear 104. This is because it occurs at wavelengths at whichthe eyewear transmission should be high to ensure efficient transmissionof the corresponding image.

FIG. 4C is a graph showing scaled spectra for an RGB color filter arrayincorporated into a light modulating panel. Each profile preferablyprovides high throughput to the corresponding set of LED (or otherspectral emitter) emission bands (e.g., R1R2), while simultaneouslyproviding high density blocking of the remaining four primaries (e.g.,G1G2B1B2) to maximize saturation. When operated in the enhanced colorgamut mode, the product of a CFA spectrum, with the corresponding set ofemission bands preferably provides an acceptable color coordinate, whilesimultaneously providing high throughput. Moreover, the transition slopeand stop-band blocking density are sufficient that leakage of theremaining four primary emission bands does not unacceptably desaturatethe color coordinate. In one disclosed embodiment, referring back toFIG. 4C, the color filter array spectra are tailored to the specificcenter wavelengths of the spectral emitter emission bands. For instance,an AMLCD illuminated by a particular set of R1G1B1 primaries, producesgreatest saturation of, say, B1, when the blue filter of the colorfilter array (CFA) provides high optical density absorption of theremaining R1G1 emission. Similarly, the greatest saturation of G1 occurswhen the green filter of the CFA provides high optical densityabsorption of the remaining (R1B1) emission, and so on. When thealternate set of primary bands is displayed, a similar argument applies.

Since dye filters typically used for the CFA have limited transitionslopes (as well as blocking density versus throughput), the carefulselection of center wavelengths of the primary bands are important tothe saturation of the resulting color coordinates. Since six bands arepacked into the same wavelength range, enjoying maximum gamutenhancement may be limited by the CFA spectral performance.

FIG. 4D is a graph showing spectra of first and second sets of spectralemitters through a color filter array. The corresponding colorcoordinates, are represented by points 452, 454, 456 in FIG. 4E, whichis an EBU graph showing a light output set defined by an RGB triangle ina modified color space (u′, v′). Some reduction in the short green (forexample, G2) emission may be warranted in order to further saturate thelong blue primary (for example, B1).

Using six primary spectral emitters, there are four possible groupingsof primary bands. For example, although the first spectral emitter setis described in an embodiment as R1G1B1, and the second spectral emitterset is described in an embodiment as R2G2B2, other combinations ofspectral emitters are feasible. FIG. 4F shows another combination,corresponding to a first spectral emitter set (R2G1B2) and a secondspectral emitter set (R1G2B1). This graph shows the sequential whiteillumination spectra that are input to the panel. Alternative groupingsfor spectral emitter sets include R1G1B2/R2G2B1 and R2G1B1/R1G2B2.

FIG. 4G shows the resulting six primary color spectra of FIG. 4F, givenas the product of a particular white input spectrum with each of theColor Filter Array spectra (shown in FIG. 4C). The corresponding colorcoordinates are shown in FIG. 4H, which is an EBU graph showing firstand second light output sets corresponding to the spectral emittersreferenced in FIG. 4G, as defined by first and second RGB triangles in amodified color space (u′, v′). Here, a first set of spectral emittersprovides a first light bundle defined by a first RGB triangle 462 of anEBU color gamut diagram, and the second set of spectral emitters providea second light bundle defined by a second RGB triangle 464 of the EBUcolor gamut diagram including colors outside the first RGB triangle,such that the enhanced display mode provides an enhanced color gamut tothat produced by one light bundle.

In principle, a display operating at 120 Hz will produce a time-averagedoutput, so the actual grouping is not critical to performance. Atime-averaged brightness and white point will result. Subtleties thatcan come into play include the details of the overlap of spectra indetermining the saturation of the primaries. For instance, it may bepreferable to group (B2G2) and (B1G1) in order to minimize theconstraints on the CFA in separating the blue and green primaries. Inaddition, it may be beneficial to match the luminance of the whiteoutput spectra, in order to mitigate any flicker effects.

In principle, the grouping used to implement multi-primary display candiffer from that used in stereo mode. It simply depends upon practicalissues regarding flexibility incorporated into the backlight forindividually addressing the LEDs.

In stereo mode, substantially non-overlapping spectral filters are usedto decode first and second images for left and right eyes respectively.FIG. 4I is a graph illustrating transmission profiles for an embodimentincluding first and second polarization interference filters for viewingrespective first and second images illuminated with respective first andsecond sets of spectral emitters. An image for the left eye is providedvia a retarder stack, with a first duty ratio, followed by an analyzingpolarizer that is parallel to the LCD polarizer. An image for the righteye is provided via a retarder stack with a second duty ratio, followedby an analyzing polarizer that is crossed with the LCD polarizer. Notethat the parallel/crossed arrangement, with identical film retardanceused in each stack, ensures that the spectral overlap point is fixed bythe relative duty ratio of the designs.

FIG. 4J shows the raw spectra from the spectral emitters transmitted toeach eye through the aforementioned polarization interference eyewear ofFIG. 4I. FIG. 4K shows the scaled version of the FIG. 4J spectra,adjusted to achieve balanced white lumens and color in each eye. Atechnique for optimizing eyewear filter designs to achieve balancedwhite lumens and color in each eye involves maximizing net brightnessafter suitable color correction. Acceptable color corresponds to eacheye seeing acceptable primary colors (RGB) with a corrected full white(D65). The brightest channel can then be attenuated to allow for matchedleft eye/right eye brightness. Under these conditions, each eye can bemade to experience effectively the same primary color hues byselectively adding small proportions of two display primaries into anoversaturated third.

FIG. 4L is a graph illustrating transmission profiles for anotherembodiment including first and second polarization interference filtersfor viewing respective first and second images illuminated withrespective first and second sets of spectral emitters. In thisembodiment, a first filter's transmission spectrum allows a first lightbundle (R1,G1,B2) to be transmitted, and a second filter's transmissionspectrum allows a second light bundle (R2,G2,B1) to be transmitted. Inaccordance with the present disclosure, the first filter blocks thespectral frequencies of the second light bundle, and the second filterblocks the spectral frequencies of the first light bundle.

Types of Spectral Emitters

As mentioned earlier, various types of spectral emitters may be used toprovide backlight illumination for a direct-view display in accordancewith the present disclosure. While LEDs are described throughout as thespectral emitters used in the described embodiments, consistent with thepresent disclosure, other suitable spectral emitters may be used such aslasers and super resonant LEDs (or sub-threshold lasers). Such spectralemitters provide several benefits in implementing next-generationdisplays, including narrow spectral emission, rapid modulation,convenient packaging in sub-arrays, long lifetime—and being mercuryfree, they are more environmentally acceptable than CCFLs. Theaforementioned spectral emitters provide operational advantages withregard to rapid modulation. Since the response time of an LED is mainlylimited by the driver (typically microseconds), pulsing can be used tooptimize power efficiency/thermal management, and manage temporalartifacts of the modulating panel. Other benefits, such ascontent-dependent dimming, and active color temperature control may befeasible due to the independence in electronic control of thesynthesized spectrum. In addition, LEDs lend themselves to buildingsub-arrays or packaged clusters for implementing scanning-backlightsystems, which advantageously provide minimized temporal artifacts.Further, the long lifetime typical of most LEDs, and their mercury freeconstruction provide advantages over conventional CCFL technology. Theabove features provide initiative for a migration from Cold CathodeFluorescent Lamps (CCFL) to backlight systems with spectral emitters(for example, LEDs, super resonant LEDs, and lasers), particularly forhigh performance video.

Spectral emitters suitable for the above functions can take many forms.For example, organic light emitting diode (OLED) stripes can bepatterned and or stacked on a substrate in a periodic fashion (e.g., R1,R2, G1, G2, B1, B2). In some embodiments, the spectral emitter sets 310,320 may be directly optically coupled to the light modulating panel 202,while in other embodiments, the spectral emitter sets 310, 320 may beoptically coupled to the light modulating panel 202 via opticallytransmissive components that include light guides, light pipes, fiberoptics, reflectors, wave guides, et cetera. Such optically transmissivecomponents may be plastic, glass, silica on silicon-based, or acombination thereof. Discrete LEDs can also be packaged in linear arraysmounted directly behind the panel, or coupled into light guides from oneor more edges. Techniques for providing uniform illumination of themodulating panel are well known, using edge illumination and lightguides, or arrays of LEDs mounted behind the panel.

Addressing Problems with Motion Artifacts in LCD Displays

The representation of motion has heretofore been an issue withconventional LCD displays. Contributing factors include, first, theresponse of typical LCD panels being too slow, and second, the hold-timeeffect of a display. With regard to the first factor, in conventionalLCD displays, a TFT panel is addressed in a scrolling row-by-rowfashion. Once an electric field is applied across the LC layer, severalmilliseconds are required for the LC material to reorient between statesrepresenting the gray level difference between consecutive images.During continuous illumination, a moving object can thus appear to havea poorly defined location during this transition, resulting in aperception of image smearing. One technique to reduce this motionartifact problem involves developing faster switching LC materials,alignment recipes and structures (e.g. multi-domain) and addressingschemes (e.g. overdrive).

It is known, however, that a hold-type display operating at 60 Hz willdemonstrate perceived image blurring under any circumstances. At certainspatial frequencies, there is an almost complete loss in perceivedcontrast that occurs even when infinitely fast switching LC is assumed.To combat this problem, redesigns in the panel are underway in theindustry to operate at 120 Hz. At such frequencies, alternate images maybe inserted via on-the-fly interpolation between bracketing images. Suchmeasures are difficult and expensive, but they also enable somemulti-functional displays by allowing, for example, flicker-free stereodisplay.

Perceived blurring from the hold-type displays notwithstanding, fasterLC switching is also desirable for reducing motion artifacts. Presently,panel response time has improved significantly, with 4 ms being fairlystandard in high-end displays. This will undoubtedly improveincrementally over time. Such switching speed is also desirable forrealizing multifunctional displays in accordance with the presentdisclosure.

Addressing the hold-time effect, other techniques that mitigate motionartifacts involve modulating the illumination. Sluyterman et al. teachthe use of a CCFL with black frame insertion to reduce motion blurring.However, this technique using CCFLs introduces serious problems. WhileCCFLs can in principle be used to eliminate light loss/efficiencyissues, another problem exists: Operation at 60 Hz with black frameinsertion introduces flicker.

Considering the above-referenced limitations connected with finite LCswitching, the scanning function using spectral emitters disclosedherein may be desirable to optimize the timing of illumination, suchthat the illumination follows the panel addressing. A scrolling blackband can minimize, if not eliminate the appearance of before/after ghostimages. Several individually addressable sub-arrays of LEDs (oralternative spectral emitters) can be used to create multipleillumination segments. In embodiments, for the purposes of timingoptimization, a course grouping of sub-arrays (e.g., 3-10) may be used.Note that black band cycling at 60 Hz can also introduce some flicker.

FIG. 5 is a schematic diagram illustrating a scanning backlightutilizing a black-band insertion technique. FIG. 5 illustrates adirect-view display at various stages in time cycles t0 through t5,represented by simplified display shots 510, 520, 530, 540, 550, 560respectively.

FIG. 6 is a logic diagram illustrating a process of black band insertionin conjunction with the scanning backlight illustration of FIG. 5. Attime to, first image 510 is fully displayed and illuminated by R1G1B1spectral emitters, at step 602. At time t1, the R1G1B1 spectral emittersare turned off in sub-array 502 (at step 604) and the liquid crystalmolecules associated with sub-array 502 are reconfigured to display asecond image (step 606). At time t2, the R2G2B2 spectral emitters insub-array 502 are turned on to display the first portion of the secondimage illuminated with R2G2B2 primaries (step 608). Prior to,simultaneously, or subsequent to step 608, the R1G1B1 spectral emittersare turned off in sub-array 504, at step 610, as the liquid crystalmolecules associated with subarray 504 are reconfigured for the secondimage (step 612). Similarly, at time t3, image 530 illustrates theR2G2B2 spectral emitters in sub-array 504 being turned on to display thesecond portion of the second image in R2G2B2 primaries (step 614). Thissequence continues in a similar fashion with regard to images 540 and550, until time t5, when the second image is fully displayed in R2G2B2primaries (step 616). Following that, the sequence repeats to show thenext frame of the first image, again using the first set of spectralemitters R1G1B1 for illumination. First and second images can correspondeither to six-primary data, to left/right perspectives of a stereoimage, to the two images of a privacy screen display, or achannel-multiplexed display.

In another embodiment, a first set of spectral emitters may not beturned all the way off, but may provide a reduced-intensity output thatis barely visible through the filter that is designed to pass theemission spectra from the first set of spectral emitters. Similarly, inanother phase of the duty cycle, the second set of spectral emittersneed not be entirely turned off. Thus, such an embodiment may allow thespectral emitters to be partially biased when they are in their‘off-cycle,’ rather than being entirely turned off. This may allowfaster switching between illumination/non-illumination states since therespective spectral emitter sets will already be partially biased whenin the non-illumination state.

FIGS. 7A-7H illustrate a sequential illumination of sub-arrays 702-708for first and second sets of spectral emitters 710, 720 in a backlight700. FIG. 7A shows a first set of spectral emitters 710 in a firstsubarray 702 providing illumination. In sequence, FIG. 7B then shows afirst set of spectral emitters 710 in a second subarray 704 providingillumination. The sequence for the first set of spectral emitters 710continues in turn through FIGS. 7C and 7D. Following that, FIG. 7E showsa second set of spectral emitters 720 in a first subarray 702 providingillumination—and in sequence, illumination of the second set of spectralemitters 720 in second subarray 704, third subarray 706, and fourthsubarray 708, as shown by FIGS. 7F-7H respectively.

FIGS. 8A-8H are schematic diagrams illustrating another embodiment of anLED-based scanning backlight 800 with light control films 840. Thesequence of operation in this embodiment is similar to that shown abovewith reference to FIGS. 7A-7H. In this embodiment, light control film840 may provide filtering, and dispersion of the light from each set ofspectral emitters to provide homogeneity in illumination, particularlyin the vicinity of the respective barriers between the subarrays. Lightcontrol film 840 may also provide matching of LED luminance andchrominance in the sub-arrays 802, 804, 806, 808.

Note that the actual operation of the LED array is largely dependentupon the functionality of the panel. For panels that are capable ofglobal-update at fast enough rates, such a scanning backlight techniqueusing sub-arrays may be avoided and the illumination can operate in ablinking mode with little sacrifice in brightness. In such cases, theilluminator simply alternates between flood-illuminating the panel witheither of two sets of primaries (for example, simultaneously flash allR1G1B1 spectral emitters, then flash R2G2B2 spectral emitters, etcetera). A black interval can be inserted between frames to allow the LC(light modulating panel) to settle. The extent of the blanking function(if used) depends upon the response time of the panel. In aprogressive-scan panel, a blinking backlight can also be used, thoughthere is some additional sacrifice in brightness.

Enhanced Color Gamut Mode

A display using a backlight 300 in accordance with the presentdisclosure is capable of producing a much richer color palette thanconventionally backlit displays using CCFLs or three-primary LEDbacklights. As discussed previously, a six-primary gamut with improvedsaturation of each primary may be achieved in an enhanced gamut mode.Through careful selection of the six primary bands and the color filterarray spectra, a greatly expanded color gamut is achievable. Thispermits displaying a broader range of colors that are simply notpossible with conventional AMLCD displays.

When the backlight 300 is operated in an enhanced color gamut mode(displaying a two-dimensional picture), the benefits of two sets ofspectral emitters with different color points may be realized. In thiscase, the illuminating segments can utilize all LEDs in a sub-arraysimultaneously for maximum brightness and color gamut. In the maximumbrightness condition, the backlight 300 provides the product of R1 andR2 with the red color filter, G1 and G2 with the green color filter, andB1 and B2 with the blue color filter. When dimming is required, it canbe performed in a way that is beneficial to the color gamut for thedisplayed image(s). Current can be selectively applied to specificspectral emitters such that the color gamut is expanded. Furthermore,specific spectral emitters may be illuminated or dimmed to provideselective illumination to areas of the display requiring enhanced orreduced brightness respectively.

The above scanning backlight functionality for optimized two-dimensionaldisplay is very similar to the requirements for implementing anoptimized six-primary display, a spectral-division stereo display, aprivacy screen display, or a channel-multiplexed display. By supplyingat least two sets of RGB LED arrays in each backlight sub-array, aspectrally-switchable scanning backlight is realized. To the extent thatsequential operation is used, at least a 2.times. frame rate should beemployed to avoid flicker. Unlike color sequential displays, however,such operation should be free of the color-break up issues. This isbecause each frame contains a full representation of the image in RGB.

A six-primary display has several important applications where anenhanced gamut is beneficial. When incorporated with measures to provideaccuracy in transmitting/displaying color, such displays are alreadyvery important. Nowhere is this a more timely issue than in e-commerce,where certain products cannot be accurately marketed on the internet.This is due to inconsistency, or inability, to accurately represent theproduct appearance on conventional displays. Already, the limitations inselling fashion apparel on the internet are significant, as theappearance on a monitor does not adequately match the actual product.These situations result in mass product returns, and a general distrustamong the public in the ability to successfully carry out certainpurchases on the internet. This can extend to products such as motorvehicles, furniture, interior decorating (e.g. draperies, counter tops,flooring) etc.

The six-primary display is also an important part of the infrastructurenecessary to support next generation photography. Image capture devicescapable of six-primary capture require both image printing and displaytechnologies. Since a relatively low percentage of electronicallycaptured images are viewed in hard copy, it will be increasinglyimportant for such images to be displayed with no sacrifice in imagequality. In fact, such a system enables electronic imaging to step aheadof film photography in both performance and convenience.

Images captured with a six-color camera, and displayed on a large screensix-color AMLCD should provide a far superior experience to viewinghard-copy.

Insofar as the spectral emitters can be individually addressed, and thedisplay is sufficiently fast switching, a backlight embodiment of thepresent disclosure can also support sequential color display. In such anembodiment, the CFA is removed, such that each pixel is capable offull-color. The demands of switching speed to support multi-functionaldisplays using sequential color operation are of course greatlyincreased. A video display operated in a six-color mode probably callsfor a 360 Hz field rate to avoid flicker. However, such displays arevulnerable to color breakup effects, which can further increase fieldrate requirements.

Privacy Screen Mode

An aspect of the present disclosure includes providing a privacy screenmode of operation for the direct view display. This mode can be used toprevent others from viewing sensitive or proprietary information, withapplications including, for example, mobile computing. Such concerns canlimit the work activities of professionals traveling on airliners ortrains. It can also be used to view imagery or text that may be of apersonal nature. In the home, the privacy screen display can be used toallow adults to view programming that may not be suitable for children.It can also be used to allow viewers to watch programming withoutdistraction to others in line of sight of the display. In the lattercases, eyewear affixed with audio input can be worn so that there are nodistractions. This allows, for example, one person to watch a televisionprogram while another reads a book in the same room.

In the privacy screen mode, two sets of spectral emitters (for example,R1G1B1 and R2G2B2 LEDs) may be used to sequentially illuminate a primaryand a secondary image. The primary image, illuminated by R1G1B1 spectralemitters, is intended for viewing, while the secondary image,illuminated by R2G2B2 spectral emitters, is intended for obscuring theprimary image when viewed in natural light. The secondary image issynthesized as the inverse of the primary image, such that a neutralgray screen is observed as the time-average of the two images whenviewed in natural light. Moreover, the screen will also appearcontent-free when viewed by conventional polarizing eyewear. However, aspecialized set of wavelength-selective eyewear can decode the twoimages. The filters in the eyewear are designed to pass primarily oronly the primary image spectrum, while blocking the secondary imagespectrum.

Eyewear for use with the privacy screen mode can be fabricated usingconventional interference filter technology (formed either fromdeposition or stretching of co-extruded films), rugate filtertechnology, holographic technology, or polarization interferencetechnology. In one disclosed embodiment, both lenses are identical inconstruction; using a retarder stack, followed by a linear polarizer.Since the direct view display of the present disclosure may provide ananalyzing polarizer, the eyewear can omit any input polarizer. Since anyfiltering operation is incomplete without this polarizer, the eyewearwill appear neutral in natural (unpolarized) light. All other advantagesof polarization interference, such as improved light control (throughlack of reflection), and improved field-of-view are considered helpfulin presenting a high contrast image that is comfortable to observe forextended periods. Aspects, such as low spectral leakage of the secondaryprimary set, are key aspects to providing high contrast, since thedisplay is operated in a 50% duty ratio mode. Without the privacy-screeneyewear, secondary image ghosts, which are by definition inverse images,tend to strongly wash out the primary image.

An important aspect of polarization interference filter eyewear is thatuniform retarder stacks are realizations of finite impulse response(FIR) filters. Increased retardation in the base film has an inverserelationship with sampling rate, thus increasing oscillations in thefrequency (wavelength) domain. Such periodic comb functions are utilizedfor partitioning the spectrum according to primary set, and are anatural phenomenon in FIR filters. Through network synthesis techniques,as described in the commonly assigned U.S. Pat. No. 5,751,384, which isincorporated herein by reference, retarder stacks can be designedaccording to desired edge functions and duty ratios. Further details ofdesign approaches for retarder stacks are described in greater detail inU.S. patent application Ser. No. 09/754,091, which is herebyincorporated by reference herein.

Conversely, thin-film interference filters (such as those taught for usewith the Jorke system), which are realizations of infinite impulseresponse (IIR) filters require many layers to implement a narrow notch,with very tight control on layer thickness to meet stringent centerwavelength and band edge wavelength tolerances. Multiple notches ofcourse require stacks of individual notch filters. Multi-notchinterference filters are difficult to fabricate with tight tolerances on50% points, and are destined to be an expensive option. Moreover,filters with such high wavelength selectivity are sensitive to incidenceangle. The view angle effect allows the secondary image to bleed throughand reduce contrast and uniformity in appearance.

Multiplexed Image Mode

In accordance with another aspect of the disclosure, viewers wearingdifferent sets of eyewear can independently view different multimediaimages on the same display using time multiplexing of channels.

In a channel-multiplexed display mode, the time-averaged superpositionof imagery from two channels is observed in natural light. A firstviewer wears a first set of eyewear that passes imagery displayed in thefirst color gamut using primaries R1G1B1. A second viewer wears a secondset of eyewear that passes imagery displayed in the second color gamutusing primaries R2G2B2. Accordingly, through the respective eyewear, thefirst viewer sees imagery corresponding to a first color gamut and thesecond viewer sees imagery corresponding to the second color gamut. Tothe extent that the images as observed through the filters arespectrally non-overlapping, no ghost images of the alternate channelshould be observed. With a display operated at 120 Hz, each personindependently views a 50% duty cycle image at 60 Hz. Thus, for example,an application of the multiplexed image mode allows for watching twotelevision channels on the same direct view display, with each channelbeing presented occupying the entire screen. Another application allowsfor a first viewer watching television while a second viewer surfs theinternet A third application allows for a first video game player toview a first displayed image for a multiplayer video game, while asecond player views a second displayed image. Of course, it should beapparent that various other applications may utilize multiplexed imagemode.

Stereo Image Mode

Stereo imagery is used to create the appearance of depth on a 2Ddisplay. Unlike some other stereo display methods, such asmicro-polarizer array, the present disclosure provides three-dimensionalimagery without loss in spatial resolution. Provided that the displaycan be operated sufficiently fast to avoid the effects of flicker, asuperior 3D experience can be realized.

Through careful backlight designs, high quality 3D displays can beimplemented with practically no degradation to 2D performance, and withminimal additional hardware. A stereo display according to the presentdisclosure is operated in a similar fashion to the above-describedprivacy screen display or enhanced gamut six-primary display. In thestereo imaging mode, first and second images are sequentially presentedthat represent left-right views, which (preferably) have substantiallynon-overlapping spectral components through the action of the backlighthaving first and second sets of spectral emitters (as discussedpreviously). These views appear overlaid on the display when viewed innatural light. An appropriate set of eyewear is used to decode theimages, such that the left view image is blocked by the right lens andthe right view image is blocked by the left lens. This can in principlebe accomplished using a number of technologies, as discussed above.However, polarization interference filter technology is superior toother technologies in the aspects discussed previously.

In a described stereo display embodiment, polarization-interferenceeyewear is used to separate left and right views of an image. The lensesof such eyewear comprise a stack of linear retarder films, followed byan analyzing polarizer. According to the described embodiment, alinearly polarized output is provided by the analyzing polarizer of theAMLCD, which is oriented parallel to the polarizer in a first lens, andis crossed with the polarizer of a second lens. The retarder stackdesign is identical in the first and second lens. Furthermore, theretarder stack design, in particular the duty-ratio, is selected so asto maximize light coupling to each eye, with minimal spectral overlapbetween the lenses (which causes image cross-talk).

Eyewear Design Considerations

Unlike the privacy screen eyewear discussed previously, thestereo-display eyewear is used to alternately present different imagesto each eye sequentially. In construction, the eyewear is much asdiscussed previously. However, for stereoscopic viewing applications,the spectra associated with each left and right filters are, like theillumination source, substantially non-overlapping. The extent of ghostimage appearance (neglecting software corrections) depends largely onthe dynamic range of the filter, and the extent of spectral overlap offilters in the vicinity of LED (or other spectral emitter) emission. Themore confined the source emission (a laser being best, and a superresonant LED being the next best), the less demanding the filteringoperation needed by the eyewear. In general, improved dynamic range isdesirable, though selective sources permit a relaxation in filtertransition slope. In practice, the extent of this relaxation dependsupon tolerances in emission center wavelength in manufacturing.Accordingly, utilization of super resonant LEDs as spectral emitters mayprovide a good compromise solution that addresses the above designfactors.

An embodiment of stereo-display eyewear includes the use of retarderstacks for left and right filters using the identical retardation value.Using network synthesis techniques, as described in the commonlyassigned U.S. Pat. No. 5,751,384 incorporated by reference, the dutyratio for each lens can be selected. Referring back to FIG. 4I, thegraph illustrates transmission profiles for an embodiment that includesfirst and second polarization interference filters for viewingrespective first and second images illuminated with respective first andsecond sets of spectral emitters. The profile for each filter has aseries of steep transition slopes with flat pass-bands and stop-bands.According to the present disclosure, the duty ratio of the spectralprofile of each lens may be selected to control the extent of spectraloverlap. When the parallel polarizer spectrum of the left image isoverlaid with the crossed polarizer spectrum of the right image, aconstant overlap factor is assured. This is a consequence of usingidentical retarder films in each stack, in combination with theprinciples of conservation of power.

Such polarization-interference eyewear lenses are, much likeconventional 3D polarizing lenses, neutral in appearance, as retarderstacks are fully transparent in natural light. In that respect, theviewer will appear to be wearing matched neutral eyewear to anyobserver. To the wearer, the natural world will likewise appearidentical through each lens, and will primarily or only appear differentwhen viewing a polarized input. The lenses will thus act to diminish thebrightness of surroundings by 50%, with (neglecting the filteringoperation of the lens) little insertion loss when viewing the display.Using current high-performance linear polarizers, internal insertionlosses of polarized light is about 6% in the green.

According to an embodiment of the present disclosure, absorption-basedeyewear with highly selective spectral filtering provided bypolarization interference can be used to give optimum performance incomfort, see-through, brightness, and cross-talk. Moreover, the lensescan be formed in either cylindrical shapes, or even thermoformed forcompound curvature, to minimize field-of-view effects. Retarder stacksbased on biaxial-stretched retarder film are additionally virtuallyinsensitive to angle-of-incidence spectral shifts. Using eyewear canalso help with head tracking for full surround 3D, as the infinity pointwon't move with the user.

As discussed previously, in some embodiments, the input polarizer foreach filter may be omitted when using a display that provides a linearlypolarized output, thus there is one and only one polarizer in eachfilter. The addition of an input polarizer on each filter reduces thethroughput slightly, but it may also have an effect on the appearance ofthe natural world. (Such a filter, with an input polarizer is taught bycommonly-assigned U.S. Pat. No. 7,106,509, and is hereby incorporated byreference in its entirety). This can take the form of a luminance and/ora chrominance difference as viewed through each filter. Since a viewertypically takes in both the displayed image, and some portion of thesurroundings, the differences seen through each filter may bedistracting. Moreover, it is difficult to correct for such differences,in part because stereo displays can be viewed in a number of spectrallydistinct ambient lighting conditions (e.g., sunlight, fluorescent light,incandescent light, et cetera). While the conditions of the displayedimage can be carefully controlled, the relative appearance of thenatural world can vary dramatically when viewed through each filter. Assuch, it may be desirable to provide a left/right filter system that ismatched in chrominance and luminance under all ambient light conditions.When viewing the display, careful corrections can be applied by alteringthe spectral emissions of R1G1B1 and R2G2B2 to match the chrominance andluminance of the white point seen by each eye, which are not possible inthe natural world. By omitting the input polarizer of each filter, theseconditions are most likely to occur, insofar as the natural world isvirtually unpolarized.

A beneficial aspect of polarization interference eyewear is in contrastenhancement. The filtration of light, such that only the appropriate setof primaries (for example, R1G1B1 or R2G2B2) are allowed to pass, hasthe effect of eliminating broad band glare incident on the display fromambient sources. While the addition of an input polarizer to each lenseliminates the neutral appearance, it has the benefit of furtherincreasing contrast by rejecting the glare by blocking the orthogonalpolarization. In addition, the input polarizer minimizes the sensitivityto head tilt on image cross-talk. In this case, head tilt acts primarilyto decrease brightness of the display.

A technique for decreasing sensitivity to head tilt, without theaddition of a secondary polarizer, is to place a quarter-wave retarder(or circular retarder) on both the display and eyewear. A quarter-waveretarder, oriented at 45-degrees with respect to the polarizer on thedisplay, produces substantially circular polarization of a particularhandedness. A secondary matched quarter-wave retarder, oriented at minus45-degrees on the eyewear, has the effect of canceling the polarizationeffect of the former. The transformation from a linear to aquasi-circular coordinate system produces first-order elimination inhead tilt sensitivity. For zero-order quarter-wave retarders, theretardation values are preferably closely matched to minimize ghostimages.

In another embodiment, quarter-wave retarders are provided on both thedisplay and eyewear, as described above, with the addition of an inputpolarizer on the eyewear. In this way, cross-talk is minimized, whilesubstantially reducing the sensitivity of throughput on head-tilt. Sucheyewear may be particularly suited to the privacy screen displaysdiscussed above, where the lenses in each eye are matched. In the casewhere filters in left and right eyes are matched (e.g., in privacyscreen and multiplexed display modes), the objectionable effect ofappearance difference of the natural world does not apply.

The foregoing provides various embodiments, which are intended toillustrate the considerations that come into play with multi-functionaldisplays. It shows that a multi-functional display capable of variousmodes of operation is possible with a single backlight. It further showsthat no special film or modulator is required, adding to the cost of thedisplay, to implement multi-functional displays. A number of factorscontribute to the selection of LED backlight design to achieve abalanced output when operating in (e.g.) stereo mode. Clearly thisexample shows that the photopic response is critical to the long-redoutput requirements, perhaps arguing for a blue shift in centerwavelength. The reality is that a number of factors, including cost ofspectral emitters (versus emission wavelength), spectral broadening,availability of center wavelength and peak output power, lifetime (andchanges over lifetime), thermal management, number of each type of LED,etc., are all important practical design considerations.

As previously discussed, stereoscopic and multi view displays can becreated by providing a sequential backlight with multiple primaries asgenerally discussed, for example in, U.S. Pat. No. 8,233,034 entitled“Multi-functional active matrix liquid crystal displays” by Sharp andRobinson, the entirety of which is herein incorporated by reference.Light-emitting diode (LED) sources have limited options for centerwavelength and have wide spectral bandwidths, both due to technologyconstraints. For low stereoscopic cross-talk and wide color-gamut,narrowband sources with tuned center wavelengths are desired.

According to the present disclosure, an optical structure may providelight to a display. The optical structure may include an excitationsource operable to transmit illumination, an input filter operable toreceive illumination from the excitation source and operable tosubstantially transmit a first wavelength band of light and operable tosubstantially reflect a second wavelength band of light. The opticalstructure may also include an emitter region with emitters, wherein theemitter region is operable to receive at least the first wavelength bandlight, and the emitters are operable to be excited by at least the firstwavelength band of light and emit a third wavelength band of light andan output filter operable to receive at least the third wavelength bandof light from the emitter region, and operable to output at least afourth wavelength band of light in which the bandwidth of the fourthwavelength band of light is narrower than the bandwidth of the thirdwavelength band of light. The emitters may be tuned to emit light at awavelength longer than the light received from the input filter.

Either one or both of the input filter and output filter may be adichroic filter. The input filter, emitter region and output filter maybe completely or partially surrounded by a cavity which may be operableto receive illumination from the excitation source. The cavity mayinclude at least one of white or metallized internal walls.

The optical structure may also include an angle reducing elementoperable to receive illumination from the emitter region, in which theangle reducing element may be prismatic tape. The optical structure mayalso include an angle transforming non imaging optic operable to receiveillumination from at least the excitation source and which may be one ofa light pipe or compound parabolic concentrator. Additionally, theoptical structure may include an angle increasing element operable toreceive light from the output filter. An optical spacer may be locatedin the optical structure between the output filter and at least a firstlight guide plate. Further, an integrator may be located between theexcitation source and the input filter.

The optical structure may provide light to a display and the display mayreceive addressing for a stereoscopic image. A first light guide plateand a second light guide plate may be scrolled so that a left image anda right image may be illuminated by spectrally separated sources.

Also, according to the present disclosure a method for backlighting adisplay may include providing at least a first wavelength band of lightfrom an illumination source, receiving the first wavelength band oflight at an input filter and transmitting the first wavelength band oflight through the input filter and receiving the first wavelength bandof light at an emitter region and exciting emitters in the emitterregion thereby producing at least a second wavelength band of light andtransmitting at least some of the first wavelength band of light throughthe emitter region. The method may also include receiving the at leastsecond wavelength band of light at an output filter and outputting athird wavelength band of light in which the bandwidth of the thirdwavelength of light may be narrower than the bandwidth of the at leastsecond wavelength of light. The method may further include receiving atleast some of the first wavelength band of light from the emitter regionat an output filter and transmitting a fourth wavelength band of light,wherein bandwidth of the fourth wavelength band of light is narrowerthan the first wavelength band of light from the emitter region. Theinput filter may receive a third wavelength of light produced by theemitter region. Wavelengths outside of the bandwidth of the thirdwavelength band may be directed back towards the emitter region by theinput filter.

Continuing the discussion, the method for backlighting a display mayinclude receiving the wavelengths of light outside of the bandwidth ofthe third wavelength of light at the emitter region which may exciteemitters in the emitter region and produce light within the bandwidth ofthe third wavelength of light. The third wavelength of light may bedirected back towards the output filter. The output filter may directlight to at least a first light guide plate and address a stereoscopicimage to a display. The light guide plates may be scrolled so that afirst image and a second image on the display are illuminated byspectrally separated sources. The right and left images may be separatedby a dark band of illumination during the display switching period forhigh contrast.

Further to the present disclosure, adjacent passbands may be placed instereoscopic eyewear and the output filter, in which the passband of theoutput filter may be red-shifted relative to the passbands of thestereoscopic eyewear.

Generally discussed herein, is an optical structure as a narrowband,highly color saturated light source for a liquid-crystal displaybacklight. The light source for the optical structure may include anexcitation source such as a blue LED. Although the excitation source maybe discussed herein as a blue LED, the excitation source may be anysource with the appropriate energy to excite the emitters in the emitterregion. Also, the terms excitation source, light source, andillumination source may be used interchangeably herein for discussionpurposes only and not of limitation.

The optical structures may provide light to light guide plates and maybe used as a backlight for liquid crystal displays. In one example, morethan one optical structure may produce two sets of colors, for exampleR1G1B1 and R2G2B2, which may be used in a stereoscopic backlit liquidcrystal display. The optical structure may be used to produce a brighterbacklight structure through light recycling of the wider bandwidth lightback into the optical structure.

In one embodiment, quantum dots may be used with an excitation source,such as an LED, to create tuned, narrowband sources of light for use ina backlight, providing a wide color gamut and low stereoscopiccross-talk. Quantum dots or phosphors may be emitters engineered to havea particular approximate center wavelength and narrow spectraldistribution. The quantum dot emitters, along with supplemental lightsources, can form the appropriate spectral emitter groups which may beemployed for a multi-functional display. In one example, the spectralemitter groups that may be formed may be R1G1B1 and R2G2B2. Thesupplemental light sources may be, but are not limited to LEDs, lasers,laser diodes, semiconductor sources, any combination thereof, and soforth.

The optical structure may include an input filter, an emitter region,and an output filter. This optical structure may produce more saturatedcolors for a wider display color gamut.

Furthermore, the optical structure may produce a brighter backlightstructure through light recycling of the wider bandwidth light back intothe optical structure. Light recycling will be discussed in detailherein.

In one example, the output filter may transmit one band of wavelengths,for example λ_(blue1)+/−Δλ_(blue1), and reflect another band ofwavelengths, for example λ_(yellow1)+/−Δλ_(yellow1). The emitter regionmay include emitter material such as phosphors or quantum dots and maybe excited by short wavelength light such as Δ_(blue1)+/−Δλ_(blue1).Continuing, the emitters or emitter material may be tuned to emit lightat one or more particular longer wavelengths such asλ_(green1)+/−Δλ_(green1), and/or λ_(red1)+/−Δλ_(red1). Further, theoutput filter may transmit one or more bands of wavelengths, for exampleλ_(blue1)+/−Δλ_(blue11), λ_(green1)+/−Δλ_(green11), and/orλ_(red1)+/−Δλ_(red11)). The bandwidths of transmitted light may besubstantially narrower than the input light. The light or wavelengthsoutside of the narrowed bands may be reflected by the output filter backtoward the emitter region and input filter. As such, this light mayexcite emitter material in the emitter region and produce light whichcan transmit through the output filter. Additionally, the lightgenerated from the emitter region traveling back toward the input filtermay be reflected by the input filter toward the output filter tosubstantially enhance the brightness of the output light.

The input and/or output filters of the optical structure may be dichroicfilters constructed using thin film deposition technology. Part of theoptical structure may be contained in a reflective cavity. Thereflective cavity may have white or metallized walls for increasing theexcitation light in the emitter region and for increasing the amount oflight exiting the output filter as indicated and discussed with respectto at least FIG. 16 herein.

Generally, an integrator may be placed between the excitation sourcesuch as LEDs, and input filter to substantially homogenize theexcitation light prior to reaching the emitter region as depicted anddiscussed with respect to at least FIG. 15. The integrator may be awhite-walled cavity, light pipe, and/or diffuser which will be discussedin detail herein.

An angle reducing element may be included in the optical structure. Thisangle reducing angle may be any type of prismatic tape such as the 3MBEF II tape. Generally, angle reducing optical elements may be prismaticfilms, molded structures, cylindrical lens arrays, spherical lensarrays, any combination thereof, and so forth. An angle transformingelement may also be included in the optical structure. The angletransforming element may be a non-imaging optic such as a tapered lightpipe or compound parabolic concentrator. The angle transforming elementmay be placed between the emitter region and output filter to controlthe angles of incidence of light at the filter plane for less filtercutoff angle shift as illustrated in at least FIG. 15 and discussedherein.

The optical structure may also include an angle increasing element. Theangle increasing element may be any of a diffuser film, roughenedoptical surface, lenticular lens film individually or any combinationthereof and so forth. The angle increasing element may be located afterthe output filter to improve the uniformity of light entering the lightguide plate portion of the backlight as indicated and discussed withrespect to at least FIG. 15 herein.

Also included in the optical structure may be an optical spacer. Theoptical spacer may be an optically thick plate and may be includedbetween the output filter and light guide plate to allow substantiallyseamless abutting of optical structures along the side of a light guideplate. This is indicated and discussed with respect to at least FIG. 19herein.

The optical structure may be employed as an illumination source forlight guide plates and a display. The display may be a multi-functionaldisplay and may display 2D or stereoscopic images. Using this opticalstructure, a stereoscopic image may be addressed to the display or LCDand the backlight may be scrolled such that left and right eye images onthe LCD may be illuminated by spectrally separated sources. Thesespectrally separated sources may be provided by separate opticalstructures. The separate optical structures may provide light to lightguide plates. One optical structure may provide light to one or morelight guide plates and one or more optical structures may provide lightto one light guide plate, or any number of optical structures mayprovide light to any number of light guide plates. The left and righteye images may be separated by a dark band of illumination during the LCswitching period for high contrast and low stereoscopic crosstalk asdepicted and discussed with respect to at least FIG. 20 herein. Theseparate two or more optical structures may produce at least two sets ofcolors, for example R1G1B1 and R2G2B2. These optical structures may beused in a stereoscopic backlit liquid crystal display as depicted anddiscussed with respect to at least FIG. 20.

In one example, the spectrally distinct optical structures mayilluminate the same light guide plate, and may be driven in atime-sequential fashion to illuminate the light guide plate in synchronywith left and right eye images which may be sequentially driven to theliquid crystal display panel. This is illustrated and discussed withrespect to at least FIG. 20.

Further to the discussion of stereoscopic systems, spectral gaps may beplaced between adjacent passbands in stereoscopic eyewear and the outputfilter. The spectral gaps may be approximately 5 nanometers. Thepassbands of the output filter may be red-shifted relative to theeyewear passbands to provide low stereoscopic crosstalk across a widerange of light angles of incidence at the output filter as depicted anddiscussed with respect to at least FIG. 17.

As illustrated in FIG. 10, sources and quantum dots for each spectralemitter group may be stacked vertically at both ends of the light guideplate (LGP). FIG. 10 is a schematic diagram illustrating an embodimentof a backlight structure. The backlight structure 1005 of FIG. 10includes a light source 1000, a pass filter 1010, an emitter region1020, a trim filter 1030, a diffuser, 1040, and light guide plates 1050.The light source 1000, as well as the pass filter 1010, the emitterregion 1020, the tri filter 1030, and the diffuser 1040, may be locatedat both ends of the LGPs to illuminate the LGPs from both sides duringany particular image frame, thus creating a more uniform illuminationsource. Although the light source 1000 is illustrated in FIG. 10 as LEDsand discussed herein as LEDs, the light source 1000 may be anyappropriate light source including, but not limited to, LEDs, lasers,laser diodes, semiconductor illumination sources, any combinationthereof, and so forth. In FIG. 10, the pass filter 1010, emitter region1020, and trim filter 1030 may be included in a cavity. The cavity willbe discussed in further detail herein.

Continuing the discussion of FIG. 10, the light source 1000 may provideillumination to the pass filter 1010, which may transmit a wavelengthband. In one example, the pass filter 1010 may be a blue pass filter.The pass filter 1010 may be any appropriate filter that provides theappropriate wavelengths. Further, the pass filter or passband filter maybe any input filter operable to transmit a first wavelength band andoperable to reflect a second wavelength band. In one example, shortwavelength light may be provided to the emitter region and operable tofunction as an excitation source to the emitter or emitter material inthe emitter region. In this example, the transmission wavelength bandmay be an approximate range of 400-480 nm and a reflective wavelengthband may be an approximate range of 480-700 nm. The transmittedwavelengths or wavelength band may then be provided to the emitterregion. The wavelength band may function to excite the emitter material.The emitter material may be phosphors or quantum dots, and may beexcited by short wavelength light. Furthermore, the emitters may betuned to emit light at one or more predetermined wavelengths, in whichthe one or more predetermined wavelengths may be longer than theexcitation wavelength. The quantum dots may also be denoted herein asand/or referred to as “QR” or a quantum rail. Additionally, the termsemitters and emitter material may be used interchangeably herein. Theoutput filter may be operable to transmit one or more wavelengths inwhich the transmitted wavelengths may have narrower bandwidths than theinput light wavelengths.

Once the wavelength band is provided to the emitter region, the emittersmay be excited by the short wavelength light and produce the appropriatewavelengths or wavelength bands or colors for a backlight. Thewavelength bands may be broader than the desired narrow bandwidth, thusthe trim filter 1030 may be employed. The trim filter may serve tonarrow the emission wavelength bands received from the emitter region tothe appropriate narrow wavelength bands employed by the LGPs. Some ofthe wavelengths may not pass through the trim filter as the wavelengthsmay not be within the appropriate narrow wavelength band transmittedthrough the trim filter. These wavelengths outside the narrow band maybe “color recycled” and reflected back into the emission region and mayserve to excite the emitters in the emission region to produce morelight. This light may exit out back to the trim filter.

At the LGP entrance face as illustrated in FIG. 10, a diffuser oruniformity controlling film 1040 (such as the Uniformity Film offered by3M Corporation) may be air-spaced near, proximate to, attached to,molded to, any combination thereof, and so forth, by the LGP forincreasing the angle of incidence's (AOI's) illumination inside the LPG.This allows for substantially uniform illumination distribution insidethe LGP over a short optical path. The diffuser 1040 may be an optionalelement to the backlight.

As indicated in FIG. 10, the pass filter 1010 may be attached to theemitter region 1020 by an adhesive 1060. Similarly, the emitter region1020 may be attached to the trim filter 1030 and the diffuser 1040 maybe attached to the LGPs via an adhesive 1060. The adhesive may be anyappropriate adhesive including, but not limited to, pressure sensitiveadhesive tape, epoxy, UV glue, any combination thereof, and so forth Tonote, although in FIG. 10 the adhesive between the pass filter andemitter region, between the emitter region and the trim filter, andbetween the diffuser and the LGPs are all labeled as 1060, they may ormay not be the same adhesive.

Although FIG. 10 illustrates only nine LEDs that comprise theillumination source, fewer light sources or more light sources maycomprise the illumination source. Likewise, although there are threelight guiding panels, more LGPs, or fewer LGPs may be employed asappropriate. The quantum rail and the pass filter are depicted as threeelements, for illustrative purposes only and not of limitation. Theremay be any number of quantum rails in the optical structure. The numberof quantum rails may be primarily related to the vertical resolution ofa panel, for example 1920×1080. In one embodiment, less than ten quantumrails may be employed in the optical structure. Additionally, althoughthere are breaks illustrated between the quantum rails and the passfilters in FIG. 10, this is for illustrative purposes only and not oflimitation. In the optical structure, breaks may be present, but may notcause a significant loss of uniformity. FIG. 11 is a schematic diagramillustrating another embodiment of a backlight structure, similar toFIG. 10. As illustrated in FIG. 11, another embodiment of a backlightstructure 1105 may include an illumination source 1100, a pass filter1110, an emission region 1120, a prismatic film 1125, a trim filter1130, a diffuser 1140, and LGPs 1150. Similar to FIG. 10, the backlightstructure 1105 also includes adhesive 1160.

As shown in FIG. 11, a prismatic film 1125 (such as BEF film offered by3M Corporation) may be placed between the quantum dots and trim filterto control the angles of incidence through the trim filter. he quantumdots or emission region 1120 and pass filter 1110 may be integrated intothe entrance of the prismatic film and similarly, the trim filter 1130may be integrated into the prismatic film exit face. For example, thecoatings may be deposited on the prismatic structure instead of making aseparate plate for the coatings. Either one or both of the emissionregion 1120 and pass filter 110, and/or trim filter 1130 may beintegrated into the prismatic film entrance and exit, respectively.

In yet another embodiment, the trim filters may be dichroic or polymericfilters may be added to the backlight structure to further narrow theemission in a particular color band, thus preventing undesirableemission resulting in desaturated color and stereo cross-talk asillustrated in FIGS. 10 and 11. If the trim filter is located at one endof the light guide plate, it also may serve to substantially reflectemissions of the other spectral emitter group located on the oppositeside of the LGPs, back into the light guide plate, thus preventingundesirable emission resulting in desaturated color and stereocross-talk.

Thickening the LCD's color filter array can also improve the narrowbandemission and prevent adjacent or nearby colors from desaturating thecolor of interest.

As illustrated in both FIGS. 10 and 11, a pass-band filter may belocated between the excitation or illumination source and the emissionregion or quantum dots. The passband filter may serve to substantiallyreflect light emitted from the quantum dots away from the excitationsource and toward the light guide plate. Further, the passband filtermay be any input filter operable to transmit a first wavelength band andoperable to reflect a second wavelength band. In one example, theexcitation source may be a blue LED, although the excitation source maybe blue or ultraviolet. Generally, for phosphors and quantum dots, theappropriate excitation wavelength may be lower than the emissionwavelength.

The transmission of dichroic trim filters may be dependent on the angleof incidence (AOI) of light entering the filter. The transmission bandsmay shift toward the blue part of the spectrum as the AOI increases.This can cause stereo cross-talk between the two eye views. Anon-imaging optic (NIO) may be inserted between the substantiallyisotropically emitting quantum dots and trim filter to transform theemission from a high AOI source to a lower AOI source, thereby improvingstereo contrast as illustrated in FIG. 12.

FIG. 12 is a schematic diagram illustrating another embodiment of abacklight structure 1205. As shown in FIG. 12, the backlight structure1205 includes illumination sources 1200, the pass filters 1210, theemissions region 1220, the non-imaging optics 1225, the trim filter1230, the diffuser 1240 and the LGPs 1250. Similar to FIGS. 10 and 11,the backlight structure 1205 also includes adhesive 1260. The NIO maytake the form of, but is not limited to, a tapered light pipe, acompound parabolic concentrator (CPC), a lens, any combination thereof,and so forth. In the case of the tapered light pipe or CPC, the tapermay be in one or two dimensions and the structure may be filled withglass, plastic or air. If the NIO is tapered in one dimension, the angleof light in the approximately orthogonal dimension at the output of theNIO may be primarily controlled with a prismatic structure molded intothe exit face of the NIO. Also, as illustrated in FIG. 12, the emissionregion or quantum dots 1220 may be integrated into the NIO. In FIG. 12,a gap is illustrated between the trim filter and the NIO. The trimfilter and the NIO may be butt coupled together such that a substantialamount of the light may pass from the NIO to the filter. Alternatively,an adhesive layer may be between the trim filter and the NIO.

Although the pass filter is illustrated as individual elements, one passfilter for each NIO, the pass filter may be a larger filter that coversthe input area of two, three, etc . . . , or all of the NIOs.Conversely, although the trim filter and the diffuser or uniformity tapeare illustrated in FIG. 12 as a single piece, the trim filter and thediffuser may be more than one piece.

FIG. 13 is a schematic diagram illustrating an embodiment of anon-imaging optical element. As shown in FIG. 13, the quantum dots oremitter region 1320, trim filter 1330, and blue filter 1310 may each beintegrated into the NIO structure 1325. Stated differently, the bluefilter and the trim filter may be coatings on the entrance and exitfaces of the NIO, respectively. For example, the quantum dots, trimfilter and the blue filter may be integrated by providing cavities forthe quantum dot material or directly coating the filters at an exit orentrance face of the NIO as illustrated in FIG. 13. In FIG. 13, the passfilter 1310 may be created by coating the entrance face of the NIO 1325,and the trim filter 1330 may be created by coating the exit face and/orfacets of the NIO 1325.

In the case of the quantum dots integrated into the NIO, the quantumdots may be contained in an integrating cavity, formed by coating orover-molding a white exterior to a light pipe, in which one face at ornear the tapered end of the NIO is oriented substantially towards theexcitation source, and another exit face is oriented substantiallytowards the angle transforming portion of the NIO, for example at thewide end of the tapered light pipe as illustrated in FIG. 13. Asillustrated in FIG. 13, the cavity 1380 may be coated or over-moldedwhite while the tapered region of the light pipe 1390 may be uncoated.The cavity may be coated in a white material to reflect and scatter theemissions from the isotropically emitting quantum dots back into theemitting material Additionally, the tapered region of the light pipe maybe uncoated to maintain angles of incidence and enhance reflectivity inthe light pipe by using total internal reflection. The NIO may functionas an angle transforming element in the optical structure.

In the example of non-uniform illumination exiting the LGP(s), the LCDtransmission may be tapered (electronically) to compensate for thenon-uniform illumination and create a uniformly illuminated image asillustrated in FIG. 14. FIG. 14 is a schematic diagram illustrating anembodiment of an LCD transmission compensated for tapered illumination.As shown in the example of FIG. 14, the light guide plate 1450 mayprovide a non-uniform illumination. In this example, the light guideplate 1450 may provide less illumination on side A and more illuminationon side B. To compensate for this non-uniform illumination, the LCD 1455may electronically taper and may provide a higher transmission level onside C and lower transmission level on side D. As a result, the LCDdisplay may appear substantially uniform.

FIG. 16 is a schematic diagram illustrating an embodiment of a whitecavity assembly. Similar to previous figures, included in FIG. 16 is anillumination source 1600, a second diffuser 1603, a pass filter 1610, aquantum rail 1620, a prismatic filter 1625, a trim filter 1630, and adiffuser 1640. Also included in FIG. 16 is the cavity 1602, and a spacerregion 1635. The spacer region 1635 may allow for nearby cavityassemblies to be abutted at the spacer edge and provide substantiallyuniform illumination over the spacer face The illumination source 1600,second diffuser 1603, pass filter 1610, quantum rail 1620, prismaticfilter 1625, trim filter 1630, and diffuser 1640 may be contained in thecavity 1602. cavity 1602 may be a reflective cavity that may have whiteor metallized cavity walls, silvered walls any combination thereof, andso forth, for increasing the excitation light in the emitter region, andfor increasing the amount of light exiting the output filter. Further,the end walls of the quantum rail may also be reflective, white, and/ormetallized so that light may be substantially prevented from leaking,while the rest of the quantum rail may remain transmissive. Althoughonly part of the illumination sources, specifically LEDs in FIG. 16, arecontained within the cavity 1602, all of the illumination source may becontained within the cavity 1602, or light may be coupled into thecavity 1602 with the light source outside of the cavity 1602.

Eyewear for decoding imagery, for example stereo imagery, from themulti-functional display may be implemented with dichroic filters orpolymeric stacks of spectrally-dependent polarization controllingfilters. In one example and as illustrated in FIG. 17, spectral gaps,for example approximately 5 nm, may be located between adjacentpassbands in the stereoscopic eyewear and output filter of the backlightstructure. FIG. 17 is a graph illustrating a wavelength gap between atrim filters and eyewear. The passbands of the output filter or trimfilter of the backlight structure may be red-shifted relative to theeyewear passbands to provide low stereoscopic crosstalk across a widerange of light angles of incidence at the output filter.

As described herein, a backlight for a multi-functional LCD display mayinclude a wide color gamut and high stereo contrast. Additionally,better light efficiency, high color correction efficiency and goodleft/right luminance balance may be achieved.

In one embodiment, an optical structure may be a narrowband, highlycolor saturated light source for a liquid-crystal display backlight orgeneral lighting, for example, precision color lighting. The opticalstructure may also be used to produce more saturated colors for a widerdisplay color gamut and also may be used to produce a brighter backlightstructure through light recycling of the wider bandwidth light back intothe optical structure. As illustrated in FIG. 18, the optical structuremay include at least an excitation source for example blue LEDs (notshown in FIG. 18), and an input filter 1810 for transmitting a firstband of wavelengths and reflecting a second band of wavelengths.

FIG. 18 is a schematic diagram illustrating a reduction in leakage witha blue shift between a trim filter and eyewear transmission. As shown inFIG. 18, an input filter 1810 may receive initial light or illuminationfrom an excitation source or illumination source. The initial light maypass through the input filter 1810 and enter the emitter region 1820.The initial light may pass directly through the emission region andadditionally through the output filter 1830. Alternatively, the initiallight at the input filter 1810 may encounter some emitters in theemission region 1820. Once excited by the initial light, the emittersmay produce emitted light which may be a second subset of light. Theemitted light may be directed either back towards the input filter 1810or in the other direction to the output filter 1830. The emitted lightat the input filter 1810 may be reflected off of the input filter andback to the emitter region, and the light recycling process may startover. Meanwhile, the emitted light directed at the output filter 1830may be partially directed through the output filter and partiallyreflected back to the emitter region 1820. The partially reflected lightin the emitter region 1820 begins the light recycling process again.

In one embodiment, the transmitted first band of wavelengths may beλ_(blue1)+/−Δλ_(blue1) and the reflected second band of wavelengths maybe λ_(yellow1)+/−Δλ_(yellow1). The light source may also include anemitter region. The emitter material may be phosphors or quantum dots,and may be excited by short wavelength light, for example,λ_(blue1)+/−Δλ_(blue1). The emitter material may also be tuned to emitlight at approximately one or more particular longer wavelengths, forexample, λ_(green1)+/−Δλ_(green1), and/or λ_(red1)+/−Δλ_(red1). Thelight source may also include an output filter for transmitting one ormore bands of wavelengths, for example, λ_(blue1)+/−Δλ_(blue11),λ_(green1)+/−Δλ_(green11), and/or λ_(red1)+/−Δλ_(red11), in which thebandwidths of transmitted light may be substantially narrower than theinput light.

As previously described, the light outside of the narrowed bandwidthsmay be substantially reflected by the output filter back toward theemitter region and input filter, and may have an opportunity to exciteemitter material and produce light, which may then be transmittedthrough the output filter. The light generated or produced by theemitter region may also travel back toward the input filter and may bereflected by the input filter toward the output filter to substantiallyenhance the brightness of the output light. In one example, the inputand output filters may be dichroic filters and may be constructed usingthin film deposition technology. Further to this example, an anglereducing element, for example, a prismatic tape such as 3M BEF II or anangle-transforming non-imaging optic such as a tapered light pipe orcompound parabolic concentrator, may be placed between the emitterregion and output filter to substantially control the angles ofincidence of light approximately at the filter plane for less filtercutoff angle shift.

FIG. 15 is a schematic diagram illustrating an embodiment of anotherbacklight structure. Included in FIG. 15 are an illumination source1500, a diffuser 1542, a pass filter 1510, an emission region 1520, aprismatic film 1525, a tri filter 1530, a diffuser 1540, and an LGP1550. The diffusers 1542 and the diffuser 1540 are optional.Additionally, the optical structure of FIG. 15 may or may not employ theprismatic film 1525. Further, the illumination sources 1500 are noted asLEDs, but may be any appropriate illumination source as describedherein.

FIG. 15 illustrates an angle increasing element such as diffuser film1540, roughened optical surface or lenticular lens film, may also belocated after the output or trim filter 1530 to improve the uniformityof light entering the light guide plate portion of the backlight. FIG.15 also illustrates that an integrator 1507 such as a white-walledcavity, light pipe, and/or diffuser, may be placed between theexcitation source such as LEDs and input filter or pass filter 1510 tosubstantially homogenize the excitation light prior to reaching theemitter region 1520. In FIG. 15, the integrator, diffuser, blue filter,emitter, BEF sheets, and trim filter may be stacked inside of a cavityas illustrated in FIG. 16.

In one example, more than one structure may be used to produce two setsof colors, for example, R1G1B1 and R2G2B2, for use in a stereoscopicbacklit liquid crystal display as illustrated in FIG. 20. Also asillustrated in FIG. 20, the optical structures may be spectrallydistinct and may illuminate the same light guide plate, and may bedriven in time-sequential fashion to illuminate the light guide plate inapproximate synchrony with left and right eye images sequentially drivento the liquid crystal display panel. Although illustrated as a singleoptical structure paired to a single LGP, more than one opticalstructure may be paired to a single LGP and multiple LGPs may be pairedto a single optical structure, and so forth. FIG. 20 will be describedin further detail below.

FIG. 19 is a schematic diagram illustrating an embodiment of abuttingoptical structures and light guide plate sections. FIG. 19 includesoptical structure 1901A and optical structure 1902, LGP 1950 and LGP1952. Optical structures 1 and 2 may both include an illumination source1900, a cavity 1903 and a spacer 1935. The cavity 1903 may include adiffuser 1942, a pass filter 1910, an emission region 1920, a prismaticfilm 1925, a trim filter 1930, and a diffuser 1940. The elementsdepicted in FIG. 19 are comparable to similarly named elements in thefigures, examples, and embodiments previously described. Although FIG.19 illustrates only two optical structures and two LGPs, any number ofoptical structures and LGPs may be employed in any combination. Forexample, one optical structure may be associated with one or more LGPs,one LGP may be associated with one of more optical structures, of anycombination of optical structures and LGPs may be associated with oneanother.

As illustrated in FIG. 19, an optical spacer 1935 such as an opticallythick plate may be included between the output filter and light guideplate to allow substantially seamless abutting of optical structuresalong the side of a light guide plate such that the gap in illuminationmay be substantially reduced or eliminated. The optical structures ofFIG. 19 may be proximate to one another, abutting, adjacent to oneanother, and so forth.

FIG. 20 is a schematic diagram illustrating an embodiment of astereoscopic scrolling backlight structure. As illustrated in FIG. 20, astereoscopic image may be addressed to the LCD and the backlight may bescrolled such that left and right eye images on the LCD are illuminatedby substantially spectrally separated sources from separate opticalstructures. The left and right images may be separated by a dark band ofillumination during the LC switching period for high contrast and lowstereoscopic crosstalk.

As may be used herein, the terms “substantially” and “approximately”provide an industry-accepted tolerance for its corresponding term and/orrelativity between items. Such an industry-accepted tolerance rangesfrom less than one percent to ten percent and corresponds to, but is notlimited to, component values, angles, et cetera. Such relativity betweenitems ranges between less than one percent to ten percent.

While various embodiments in accordance with the principles disclosedherein have been described above, it should be understood that they havebeen presented by way of example only, and are not limiting. Thus, thebreadth and scope of the embodiment(s) should not be limited by any ofthe above-described exemplary embodiments, but should be defined only inaccordance with the claims and their equivalents issuing from thisdisclosure. Furthermore, the above advantages and features are providedin described embodiments, but shall not limit the application of suchissued claims to processes and structures accomplishing any or all ofthe above advantages.

Additionally, the section headings herein are provided for consistencywith the suggestions under 37 CFR 1.77 or otherwise to provideorganizational cues. These headings shall not limit or characterize theembodiment(s) set out in any claims that may issue from this disclosure.Specifically and by way of example, although the headings refer to a“Technical Field,” such claims should not be limited by the languagechosen under this heading to describe the so-called technical field.Further, a description of a technology in the “Background” is not to beconstrued as an admission that technology is prior art to anyembodiment(s) in this disclosure. Neither is the “Brief Summary” to beconsidered as a characterization of the embodiment(s) set forth inissued claims. Furthermore, any reference in this disclosure to“invention” in the singular should not be used to argue that there isonly a single point of novelty in this disclosure. Multiple embodimentsmay be set forth according to the limitations of the multiple claimsissuing from this disclosure, and such claims accordingly define theembodiment(s), and their equivalents, that are protected thereby. In allinstances, the scope of such claims shall be considered on their ownmerits in light of this disclosure, but should not be constrained by theheadings set forth herein.

1. An optical structure for providing light to a display, comprising: anexcitation source operable to transmit illumination; an input filteroperable to receive illumination from the excitation source and operableto substantially transmit a first wavelength band of light andsubstantially reflect a second wavelength band of light; an emitterregion with emitters, wherein the emitter region is operable to receiveat least the first wavelength band light, and the emitters are operableto be excited by at least the first wavelength band of light and emit athird wavelength band of light; and an output filter operable to receiveat least the third wavelength band of light from the emitter region, andoperable to output at least a fourth wavelength band of light in whichthe bandwidth of the fourth wavelength band of light is narrower thanthe bandwidth of the third wavelength band of light.
 2. The opticalstructure for providing light to a display of claim 1, wherein the inputfilter further comprises a dichroic filter and the output filter furthercomprises a dichroic filter.
 3. The optical structure for providinglight to a display of claim 1, further comprising a cavity surroundingat least the input filter, the emitter region and the output filter andoperable to receive illumination from the excitation source.
 4. Theoptical structure for providing light to a display of claim 3, whereinthe cavity further comprises at least one of white or metallizedinternal walls.
 5. The optical structure for providing light to adisplay of claim 1, further comprising an angle reducing elementoperable to receive illumination from the emitter region.
 6. The opticalstructure for providing light to a display of claim 5, wherein the anglereducing element further comprises prismatic tape.
 7. The opticalstructure for providing light to a display of claim 1, furthercomprising an angle transforming non imaging optic operable to receiveillumination from at least the excitation source.
 8. The opticalstructure for providing light to a display of claim 7, wherein the angletransforming non imaging optic is one of a light pipe or compoundparabolic concentrator.
 9. The optical structure for providing light toa display of claim 1, further comprising an angle increasing elementoperable to receive light from the output filter.
 10. The opticalstructure for providing light to a display of claim 1, furthercomprising an optical spacer located between the output filter and atleast a first light guide plate.
 11. The optical structure for providinglight to a display of claim 3, further comprising, an integrator locatedbetween the excitation source and the input filter.
 12. (canceled) 13.The optical structure for providing light to a display of claim 1,wherein the emitters are tuned to emit light at a wavelength longer thanthe light received from the input filter.
 14. A method for backlightinga display, comprising: providing at least a first wavelength band oflight from an illumination source; receiving the first wavelength bandof light at an input filter and transmitting the first wavelength bandof light through the input filter; receiving the first wavelength bandof light at an emitter region and exciting emitters in the emitterregion thereby producing at least a second wavelength band of light andtransmitting at least some of the first wavelength band of light throughthe emitter region; receiving the at least second wavelength band oflight at an output filter and outputting a third wavelength band oflight in which the bandwidth of the third wavelength of light isnarrower than the bandwidth of the at least second wavelength of light;and receiving at least some of the first wavelength band of light fromthe emitter region at an output filter and transmitting a fourthwavelength band of light, wherein bandwidth of the fourth wavelengthband of light is narrower than the first wavelength band of light fromthe emitter region.
 15. The method for backlighting a display of claim14, further comprising receiving a third wavelength band of light at theinput filter produced by the emitter region.
 16. The method forbacklighting a display of claim 14, further comprising directingwavelengths of light outside of the bandwidth of the third wavelengthband of light back towards the emitter region.
 17. The method forbacklighting a display of claim 16, wherein receiving the wavelengths oflight outside of the bandwidth of the third wavelength band of light atthe emitter region further comprises, exciting emitters in the emitterregion and producing light within the bandwidth of the third wavelengthof light.
 18. The method for backlighting a display of claim 15, furthercomprising directing the third wavelength band of light back towards theoutput filter.
 19. (canceled)
 20. The method of backlighting a displayof claim 19, further comprising scrolling the light guide plates so thata first image and a second image on the display are illuminated byspectrally separated sources.
 21. The method of backlighting a displayof claim 20, further comprising separating the right and left image by adark band of illumination during the display switching period for highcontrast.
 22. The method of backlighting a display of claim 21, furthercomprising placing adjacent passbands in stereoscopic eyewear and theoutput filter, in which the passband of the output filter arered-shifted relative to the passbands of the stereoscopic eyewear. 23.The method of backlighting a display of claim 14, further comprisingproducing a first set of colors R1G1B1 and a second set of colors R2G2B2by using at least two optical structures.